VATICAN CITY — Police in Canada have issued an arrest warrant for the Vatican diplomat who was recalled from the United States in a child pornography investigation, accusing him of accessing porn over Christmas last year from a church.

Police in Windsor, Ont. said Carlo Capella, 50, allegedly uploaded the child porn to a social networking site while visiting a place of worship between Dec. 24 and Dec. 27.

The Vatican recalled Capella after the U.S. State Department notified it Aug. 21 of a “possible violation of laws relating to child pornography images” by one of its diplomats in Washington.

It never identified Capella by name, but Windsor police did so in a statement announcing the arrest warrant Thursday.

The Vatican says its own prosecutor was investigating and seeking further information from the U.S.

In the statement, Windsor police accused Capella of accessing, possessing and distributing pornography. It said authorities were alerted in February that someone in Windsor had allegedly uploaded child porn using a social networking site.

They obtained records of the internet service provider and determined the dates in question.

In a statement, the Diocese of London in Ontario confirmed that it helped investigators who had suspicions of “possible violations of child pornography laws by using a computer address at a local church.”

It declined further comment, citing a police request.

The Vatican hasn’t commented beyond its initial statement, or even officially identified Capella as the recalled diplomat. Several U.S. church officials have complained that the Vatican was being less than transparent about the case.

The head of the U.S. Conference of Catholic Bishops, Cardinal Daniel N. DiNardo, urged the Holy See to be “forthcoming with more details,” a reflection of how the U.S. church still struggles with credibility problems 15 years after the sex abuse scandal erupted in the U.S.

The diplomat recall was expected to lurk in the background of an international conference in Rome planned for next week at the Pontifical Gregorian University on protecting children from online sexual exploitation, pornography and abuse.

Cardinal Pietro Parolin, the Vatican secretary of state and Capella’s boss, is set to deliver the keynote speech Tuesday on “The Holy See and its commitment to combating sex abuse online.”

Panelists at the conference, which was organized months ago, are to include top law enforcement and academic experts in the field of child protection and cybercrimes, with an entire morning devoted to “Child Sexual Abuse Online: Who are the offenders?”